Elevator speed sensor

ABSTRACT

An elevator system including an elevator car mounted for movement in a building to serve the floors therein, including upper and lower terminal floors. The speed of the elevator car is checked or monitored at predetermined positions of the elevator car as it is approaching either terminal to insure that the car is slowing down within the limits of a predetermined deceleration schedule. A new and improved low inertia, fast acting car speed sensor insures that the speed indication used by the supervisory control is correct and timely at each car position check point, within a predetermined small tolerance.

June 4, 1974 United States Patent [191 Pisatowski ELEVATOR SPEED SENSOR Primary Examiner-Bernard A. Gilheany Assistant Examiner-W. E. Duncanson, Jr.

Attorne Agent, or Firm-D. R. Lackey Inventor: Albert J. Pisatowski, Wa ne, NJ. Assignee: Westinghouse Electric Corporation,

[57] ABSTRACT An elevator system including an elevator car mounted Pittsburgh, Pa.

221 Filed: May 1, 1973 1211 Appl. No.: 356,268

for movement in a building to serve the floors therein, including upper and lower terminal floors. The s of the elevator car is checked or monitored at termine peed prede- [52] US. l87/29R d positions of the elevator car as it is .ap-

Int. B66b 5/06 pr a hing ither terminal to insure that the car slowing down within the limits of a predetermined deceleration schedule. A new and improved low inertia, fa

[58] Field of Search........

Referen es Cit d st acting car speed sensor insures that the speed in- UNITED STATES PATENTS dication used by the supervisory control is correct and timely at each car position check point, within a predetermined small tolerance.

2,874,8()6 Oplinger,. ..i......... 187/29 3 379,285 187/29 Leitz 13 Claims, 3 Drawing Figures Inn 4 ne t Vm 4. .fi mf tl nm 1. V .1 h lliT i A lll w ll n A. s o S S m m m wfi a \em m. 2 l semw 1 2 e- 2 a m was I W "Ti Hun u s M m 1 ELEVATOR SPEED SENSOR BACKGROUND OF THE INVENTION 1. Field of the Invention The invention relates in general to elevator systems, and more specifically to elevator systems having speed sensors for monitoring terminal slowdown.

2. Description of the Prior Art ln electric elevator systems of the traction type, upper and lower terminal stopping devices are provided which slow down and stop the car automatically at or near the top and bottom terminal landings. Also, when reduced stroke buffers are used, emergency terminal speed limiting devices are used to reduce the speed of the car at the upper and lower terminals should the normal terminal stopping device fail to slow the car properly as the car arrives at either terminal. Car and hatch mounted switches and cams for monitoring terminal slowdown are noisy, as the cams and switches strike one another at relatively high speeds, and they require periodic maintenance. Thus, the eddy currentcoupling type speed sensor is'preferred due to its noiseless operation, simplicity, and essentially maintenance free operation.

US. Pat. 3,379,285, which is assigned to the same assignee as the present application, discloses a speed sensor for an elevator system which uses aneddy current coupling. The speed sensor in this patent operates a safety relay toset the brake on the elevator drive machine should the'elevator car fail to slow down adjacent a terminal as intended. While the speed-switchdisclosed in this patent operates satisfactorilyfor its intended function, it would be desirable toprovide a new and improved elevator system having a new and improved elevator speed sensor incorporating an eddy current coupling. For example, the new and improved speed sensor should eliminate as much mass as possible from the operating mechanism to improve its torque to inertia ratio and provide a substantially linear response to elevator speed with minimum delay between the arrival of the elevator car at a predetermined speed and theactuation of a switchwhich is intended to operate at this speed. For example, it would be desirable to operate a switch intended, to operate at a predetermined car speed within 50 milliseconds of the time at which the car reaches this speed, either when the car is accelerating or decelerating. Further, a switch which is to be operated at a predetermined speed of the elevator car by the speed sensor should close-in and dropout within a predetermined small deviation from the specified speed value, such as within i 5% or less. A speed sensor with: (a) good linearity at the speeds to be monitored for terminal slowdown, (b) a very small amount of hysteresis on close-in and drop-out, and (c) a fast operating response once the car speed is at the specified operating speed of the switch, would permit an eddy current coupling speed sensor to accurately monitor normal terminal slowdown at predetermined positions of the car with the respect to a terminal, as well as to monitor car speed for the purpose of initiating emergency terminal slowdown procedures. The switch of the hereinbefore mentioned patent was not intended to perform such exacting functions, and its torqueinertia ratio, due in part to the'weight bias used, is such Copending application Ser. No. 276,489, filed July 31, 1972, which application is also assigned to the same assignee as the present application, also discloses a speed sensor for an elevator system which utilizes an eddy current coupling. This speed sensor is directed to solving an entirely different problem, i.e., one of developing sufficient switch acting forces and sensitivity at low elevator speeds, such as 30-150 feet/minutes, without developing excessive heat in the eddy current coupling at the rated operating speed of the elevator car. This sensor automatically decouples the magnetic field producing element from the electroconductive disc of the eddy current coupling once the elevator car speed increases beyond the range in which the speed sensor is used, i.e., to initiate pre-opening of the car and hatch doors at a predetermined speed as the elevator car approaches a landing or floor to stop, and to take corrective action should the car doors be open, or opening, when the car speed exceeds a predetermined magnitude. Thus, itsoperation is non-linear at the terminal slowdown speeds to be monitored; it is not called upon to provide a signal at relatively high car speeds within a predetermined short period of time after the car is at this speed; and, it is not calledupon to pick-up and drop-out a switch at substantially the same car speed when the car reaches this speed during acceleration and deceleration.

SUMMARY OF THE. INVENTION Briefly, the present invention is a new and improved elevator system which utilizes a new and improved speed sensor having an eddy current coupling, with the speed sensor meeting the exacting requirements necessary to monitor the speed of an elevator car at a plurality of positions as it approaches the upper and lower terminals, for both normal terminal slowdown monitoring and emergency terminal slowdown monitoring. The new and improved speed sensor is particularly useful in an elevator system which utilizes solid state control, such as the elevator system described in copending application Ser. No. 254,007, filed May 17, 1972, which now US. Patent 3,750,850, is assigned to the same assignee as 'the present application, but it is to be understood that the speed sensor. may be utilized with elevator systems, having the conventional electromechanical type floor selector and control. H

The new and improved speed sensor eliminates the need for bias in the form of an auxiliary weight, and p qvi. sub ant l y @balaneesi.fastastit ssy tet with very little inertia by utilizing a shaft member mounted for rotation upon which the magnetic field producing element of the eddy current coupling is mounted, as well as the cam members for operating switches at predetermined car speeds. The magnetic field producing element, or magnet, and the cam members, are mounted on a common shaft member in at least partial counterbalancing relation, i.e., extending outwardly from the shaft in opposite directions. First and second extension spring members are used to reduce hysteresis in the speed sensor, preventing an overshoot on acceleration, and a lag on deceleration, providing a speed sensor in which a switch will close-in and drop-out with very little deviation from a specified car speed, and which will operate within 50 milliseconds of the time the car reaches its specified speed while either accelerating or decelerating.

3 I BRIEF DESCRIPTION OF THE DRAWING ings of the invention; and

FIG. 3 is an end elevational view, partially in section, of the speed sensor shown in FIG. 2.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to the drawings, and FIG. 1 in particular, there is shown an electric elevator system of the traction type, which may utilize the teachings of the invention. Elevator system 10 includes an elevator car 12 and counterweight 14, both constrained for movement in the hoistway 16 of a building 18 having a plurality of landings or floors 20, only one of which is illustrated, to be served by the elevator car 12. The car 12 and counterweight 14 are interconnected via hoist roping 22 which is 'reeved over a traction sheave 24 driven by an elevator drive motor 26. Drive motor 26 may be mounted inthe penthouse of the building 18, shown generally byline 28. Y Elevator system' 10 includes a speed sensor 30 which actuates switches between predetermined first and second positions in response to the speed of the elevator car, which switches are connected to supervisory electrical controls, shown generally at 32. The drive machine 26 is responsive to the supervisory control 32, as indicated generally by line 33. The speed sensor 30 may be made responsive to the speed of the elevator car in any suitable manner. For example, as illustrated in FIG. 1, the speed sensor 30 may be coupled to a governer 34 disposed in the penthouse 28, and which is responsive to the speed of the car 12 via a governor rope 36. The governor rope 36 extends from the car 12,

I about an idler sheave 38 disposed in the pit or bottom of the hoistway 16, about a sheave or a wheel 40 which drives the governor 34 in accordance with the car speed, and back to the car 12. The governor 34 may be of the flyweight type,'and its details are not illustrated since its construction and operation are well known in the art. A wheel 42 disposed to be driven with wheel 40 in response to movement of the elevator car is coupled with a wheel 44 of the speed sensor 30 via coupling means 46. Wheels 42 and 44 are preferably gears and coupling means 46 is preferably a timing belt having teeth thereon for cooperating with the gears to provide a driving arrangement having very little backlash or slippage. A slack belt lever 48 is biased against the coupling means 46 to detect breakage thereof. The slack belt lever 48 operates a switch, should coupling means 46 break, which switch has contacts connected to direct apredetermined course of control action. A speed sensor 30 constructed according to the teachings of the invention is shown in detail in FIGS. 2 and 3, which are side and end elevational views thereof, respectively,

4 shown partially cut away and partially in section in order to more clearly illustrate its construction.

More specifically, speed sensor 30 includes a supporting structure 50 having a base member 52 and spaced support members 54 and 56 rising perpendicularly from the base member 52. The wheel 44 and slack belt lever 48 are rotatably fixed to an external surface of support member 56. The slack belt lever 48 is disposed to actuate a switch 58, through a sleeve member 60. Switch 58 may be a mercury switch connected to initiate some control action, such as stopping the car 12 should the belt 46 break.

Speed sensor 30 includes first and second shaft members 62 and 64, respectively, mounted for rotation. The shaft members 62 and 64 are spaced with their axes parallel with one another and aligned in the same plane, which plane is perferably vertical, as best illustrated in FIG. 3. Shaft member 62 is journaled in bearings 66 and 68 mounted in support members 54 and 56, respectively, with one end of shaft member 62 extending through support member 56 and having drive wheel 44 fixed thereto. Therefore, when the elevator car 12 moves and rotates wheel 44, shaft 62 rotates with a speed directly responsive to the speed of the elevator car. In like manner, shaft 64 is journaled in bearings 70 and 72, which are mounted in the support members 54 and 56, respectively.

The first and second shaft members 62 and 64 are coupled via an eddy current coupling 73, which includes a driving element 74 fixed to shaft 62, and a driven element 76 fixed to shaft 64. The driving element 74 includes an electroconductive armature in the form of a circular metallic disc member 78. The flat plane of the disc member 78 is disposed such that it is perpendicular to the axis of shaft 62, with the disc being mounted within an enclosure formed by the upstanding support members 54 and 56, and a pair of cooperative side members 80 and 82. Disc 78 is constructed of anelectroconductive material, such as aluminum or copper. The disc 78 is accurately held by a heavier but smaller diameter member 84, which member also functions as a heat sink.

The driven element 76 includes means 86 for producing a magnetic field in which a portion of the disc 78 rotates, such as a C-shaped permanent magnet having a high coercive force. The disc 78 has a peripheral portion located between the pole pieces of magnet 86 when the shaft 64 and the driven element 76 are in a predetermined angular location, such as with the vertical center line of the magnet 86, as illustrated in the elevational view of FIG. 3, being located on an imaginary line 88 drawn between and perpendicular to the axes of shafts 62 and 64.

Magnet 86 is disposed on one side of shaft member 64, extending outwardly therefrom on a support member 90. Support member 90 may be fixed to shaft member 64 by any suitable means, such as by screws 92. Shaft member 64 may have a square or rectangular cross-sectional configuration, starting a predetermined dimension from each end, to facilitate connecting member 90 thereto.

Shaft member 64 carries a plurality of cam members for actuating a plurality of switches. The number of cam members carried by shaft 64 depends upon the number of speed check points required. In general, the higher the car speed the more speed check points and thus the more cam members required. For example, an

elevator car which has a normal maximum operating speed of 1,400 feet per minute may require speed switches which operate at 350, 640, 910, 1,100 and 1,260 feet per minute, with these speed switches being checked, for example, when the elevator car is 3, 10, 20, 30 and 40 feet, respectively, from the upper and lower terminals. The switches for monitoring normal terminal slowdown may be separate from the switch which monitors emergency terminal slowdown; or, one of the switches for monitoring normal terminal slowdown may be used for monitoring emergency terminal slowdown by checking the condition of the switch when the car is at a closer point to the terminal than where this same switch is checked during normal terminal slowdown monitoring.

For purposes of example, it will be assumed that five different car speeds are to be detected, requiring five different cam members 100, 102, 104, 106 and 108. The cam members 100, 102, 104, 106 and 108 depend from shaft members 64 via support members 110, 112, 114, 116 and 118, respectively. Each of the support members, such as support member 110, is secured to shaft 64 in any suitable manner, such as by screws 120. Support members 110, 112, 114, 116 and 118 extend outwardly from shaft member 64 in an opposite or counterbalancing direction compared with the direction of support 90 for the magnet 86. To preclude interference between the magnet support member 90 and the cam support members, the cam support members may be secured to the surface of shaft member 64 which is opposite to or parallel with the surface to which the magnet support 90 is secured. As illustrated in FIG. 2, a line drawn through a predetermined one of the mounting screws 120 which is perpendicular to the longitudinal center line of shaft member 64 will bisect the cam surface of its associated cam member. This facilitates locating the tapped mounting holes in shaft member 64 for mounting the cam support members as the locations of the cam members and their associated switches will be fixed. It will also be noted from FIG. 3 that the mounting members for the magnet 86 and cam members are arranged such that if line 88, which extends between the longitudinal center lines of shafts 62 and 64, is assumed to be the edge of a plane, that it will bisect magnet 86, and this plane, when extended, wil bisect each of the cam members.

Since terminal slowdown of the elevator car is to be monitored for both terminals, i.e., when the car is traveling upwardly towards the upper terminal, and downwardly towards the lower terminal, the driving member 74 of the eddy current coupling 73 will rotate in one circumferential direction when monitoring the car speed during up travel, and in the opposite circumferential direction when monitoring car speed during down travel. The driven member 76 will thus move in one direction during up travel, and the opposite direction during down travel. Thus, each of the cam members are associated with first and second switches, and each cam member has first and second similarly shaped cam surfaces for actuating the first and second switches, respectively. For example, cam members 100, 102, 104, 106 and 108 are associated with first switches 122, 124, 126, 128 and 130, respectively, which switches are actuated when the elevator car is traveling in a first direction, and a like numbered plurality of second switches, such as switch 132 for cam 100, as illustrated in FIG. 3, which switches are actuated when the elevator car is traveling opposite to the first direction. It should be noted that the construction of the speed sensor shown in FIGS. 2 and 3 enables the cam member for a predetermined speed to be an integral structure, embodying the cam surfaces in a single member for two switches, one for the up travel direction and one for the down travel direction.

Each of the switches, such as switch 122, may be a microswitch with normally open contacts, or normally closed contacts, when in its unactuated condition, depending upon the specific control arrangement they are to be used in. For purposes of example, it will be assumed that the contacts of the switches are normally open, switching to their closed positions when actuated by their associated cam member. Since each of the switches, and their mounting arrangements are similar, only switch 122 and its mounting arrangement will be described in detail.

Switch 122 includes an actuating arm 134, and a roller 136 journaled in a bearing assembly carriedby the outwardly extending end of the actuating arm. Switch 122 is mounted on a support member 138, and the support member 138 is adjustably mounted on a bracket member 140. A base member 142 is fixed to the inside surface of the bottom member 52, such as by screws 1, with the base member having slots 146 formed therein for adjustably mounting bracket member 140. The slots 146 provide an X-axis adjustment for switch 122, as viewed in FIG. 3, enabling the bracket 140 to be moved in a direction perpendicular to the side members and 82. Once the position of the bracket is set, screws'148, disposed through openings in a lower flange on bracket 140, and through slots 146, may be tightened. Loosening the screws 148 permits the bracket 140 to be moved to a new position between the side members 80 and 82, if required.

A Y-axis adjustment of switch 122 is provided by screw 150 which is held captive by an upper flange portion '152 on bracket 140, and which extends into a threaded opening in support member 138. Switch 122 is fixed to support member 138 via screws 152 and 154 which extend completely through both the switch 122 and the support 138, and through spaced parallel verti cal slots 156 and 158, respectively, formed in the upstanding portion of bracket 140. A cooperative back support member 160 may be disposed on the side of bracket 140 which is opposite to the side on which support 138 is disposed, for threadably receiving the ends of screws 152 and 154. Thus, vertical adjustment of support 138 and switch 122 is accomplished by loosening screws 152 and 154, turning screw 150 to lift or lower support member 138, with the screws 152 and 154 are being guided vertically by slots 156 and 158, and then tightening screws 152 and 154 when the desired elevation of roller 136 of switch 122 is obtained.

When the disc 78 rotates counterclockwise as viewed in FIG. 3, the magnet 86 will move to pivot the drive element or magnet-cam assembly 76 clockwise about the longitudinal center line of shaft member 64, and portion of cam 100 will contact roller 136 of switch 122. Roller 136 rolls freely on its bearings to reduce friction, and when the arm 134 is depressed to the operating point of the switch 122, the contacts of the switch will change from their unoperated condition to their operated condition. The roller 136 remains in contact with surface 170 of the cam member at all speeds above the speed at which the switch was operated. The switch 122'is operated in its primary mode, as'a position switch, as opposed to a force switch, enhancing switching point accuracy and repeatablility.

However, even with the low inertia, substantially balanced rotatable structure of the magnet-cam assembly 76, substantial hystersis or difference between the close-in and drop-out points of the switch versus car speed would be experienced due to inherent friction and lag in the mechanical structure. The hystersis is reduced to percent by first and second extension spring members 180 and 182 which provide a retarding force on increasing car speed, and a restoring or aiding force on decreasing carspeed, to provide close-in and dropout of a switch within 5 percent of the nominal car speed at which the switch is'intended to close-in and drop-out. By retarding force is meant a force which opposes the movement of the magnet 86, away from its at rest angular position, and the term restoring force means a force which aids the return of the magnet to its at rest position. The extension spring members also assure that there is very little time lag, less than 50 milliseconds, between the car first reaching the nominal speed at which a switch is intended to operate, and

the actual operation of the switch. This is very important in monitoring terminal slowdown, as the condition of each speed switch is checked at a predetermined distance fromthe terminal as the car is arriving, and it is critical that when each switch is checked or. monitored that it isgiving a proper indication of whether or not the car is below or above the speed at whichtheswitch is intended to operate.

The spring members 180 are applied to the magnetcam rotatable assembly 76 on the cam side of the longitudinal center line of shaft member 64, with spring 180 being effective when the'magnet-cam assembly 76 rotates counterclockwise and spring 182 being effective when the magnet-cam assembly 76 rotates clockwise,

both as viewed in H0. 3. Thesupport member 90 upon which magnet 86 is mounted maybe constructed to extend past shaft member 64 by a predetermined dimension toward the cam members, with this downwardly extending end carrying a small shaft member 184 which extends through and. is securedin an opening near the end of support member 90, with opposite ends of the shaft member 184 having openings 186 and 188 therein for receiving the ends of springs 180 and 182, respectively. The other ends of the springs 180 and 182 are attached to support members 190 and 192, respectively, which members extend between the upright support members, 54 and 56, such that the longitudinal axes of members 190 and 192 are parallel with the axes of shaft members 62 and 64. The extension springs 180 and 182 may be secured to their associated support members 190 and 192 in a manner similar to the suport arrangement used for their other ends, utilizing small shaft members 196 and 198 which extend-through and are fixed in openings disposed in support members 190 and 192. Openings near the ends of shaft members 196 and 198 which face the rotatable driven assembly 76 of the eddy current coupling receive the ends of the springs. The support members 190 and 192 are located between the base 52 oand top portion 200 of the speed sensor such that the longitudinal center lines of the extension springs 180 and 182 are substantially horizontal. As best illustrated in FIG. 3, the spring support members 190 and 192 may have portions or legs which extend horizontally along the inner surfaces of support members 54 and 56, such as portions or legs 197 and 199, with these legs having a plurality of spaced openings therein. Thus, the initial lengths of springs and 182 may be adjusted by placing mounting screws 201 and 203 through openings in support 56 and through selected openings in legs 197 and 199 of these spring support brackets, and similar screws through similar openings in support 54 and like positioned openings in leg portions of members and 192.

The electrical contacts of the various switches are connected in control circuitry, the wires of which enter the speed sensor via a connector assembly 202, through an opening in one of the support members, such as through support member 54. The control circuitry checks each switch of a group of switches, with the group checked depending upon the travel direction of the elevator car, as the elevator approaches a terminal. For example, if the contacts of these switches are normally open, an exemplary control arrangement would connect the contacts of each switch in series with the contacts of a switch responsive to car position. These pairs of serially connected contacts would then be connected in parallel with the other pairs, and the parallel arrangement would be connected in series with a control relay. ln checking the car speed at predetermined locations of the car from a terminal, a car position switch would close and if the car speed is above the intended speed at this location, the speed switch contacts would be closed and the control relay would be energized. The specific action initiated'by the picking up of the control relay depends upon whether normal or emergency terminal slowdown is being monitored at this instance. If the car speed is below the speed of the switch being monitored, the contacts of the switchwill be open when they are checked, and the control relay will not be energized.

Since the car speeds monitored during normal and emergency terminal slowdown are relatively high, the rotational speed of disc 78 at rated car speed may be selected to be relatively low, such as 1,000 R.P.M., to prevent themagnet from being driven partially off the disc 78 and retain a linear movement of the magnet 86 with car speed. An R.P.M. of about 1,000 will also eliminate problems due to over-heating of the disc 78.

ln summary, there has been disclosed a new and improved elevator system and speed sensor therefor, which enables a car speed to be accurately indicated with very little time lag between the car reaching a predetermined speed and the switch indication of the arrival of the car at such speed. The switches operated by the speed sensor close-in and drop-out on increasing and decreasing car speeds, respectively, at speeds which are within 5 percent of the nominal speed at which the switch is intended to operate. This is due to a very low inertia rotatable assembly which includes an eddy current coupling. The driven portion of the eddy current coupling is substantially balanced about a rotational point, with a magnet of the coupling on one side of the rotational point and cams for operating speed switches on the other side of the rotational point. A slight unbalance on the side of the cams provides a restoring force to settle the coupling at the proper angular location when the elevator car is not moving. Extension spring members provide retarding and restoring forces during acceleration and deceleration, respec- 9 tively, of the elevator car, to providethe very low hystersis essential for a speed'sensor which is to monitor normal and emergency terminal slowdown.

I claim as my invention: 1. An elevator system, comprising: an elevator car, means for moving said elevator car in a predetermined path, speed sensor means including an eddy current coupling having rotatable driving and driven elements,

means translating movement of said elevator car into rotational movement of said driving element,

said driven element including a shaft member mounted for rotation, a magnetic field producing element, and cam means,

said magnetic field producing element and said cam means being mounted on said shaft member to provide at least a partial counterbalancin g relationship therebetween,

switch means disposed to be operated from a first condition to a second condition by said cam means at a first predetermined speed of the elevator car when theelevator car is accelerating, and back to its first predetermined condition at a second predetermined speed when the elevator car is deceleratmg,

control means responsive to the condition of said switch means,

said means for moving said elevator car in a predetermined path being responsive to said control means,

and spring means associated with said driven elements to provide retarding and restoring forces thereon when the speed of the elevator car is increasing and decreasing, respectively, to reduce the difference between the first and second predetermined speeds of the elevator car at which the switch means operates,

2. The elevator system of claim 1v wherein'the switch means includes first and second switches and the cam means includes a single member having first and second cam surfaces disposed to operate the first and second switches, respectively, when the elevator car is moving in first and second directions, respectively.

3. The elevator system of claim 1 wherein the magnetic field producing element is fixed to the shaft member by a first support member which extends perpendicularly-outward from the shaft member, and the cam means is fixed to the shaft member by a second support member which extends perpendicularly outward from the shaft member in a direction from the shaft member which is opposite to the direction of the first support member.

4. The elevator system of claim 1 wherein the magnetic field producing element and cam means are spaced from their supporting shaft member on opposite sides thereof, with the spring means being disposed to apply its retarding and restoring forces to a predetermined point between the shaft member and the cam means.

5. The elevator system of claim 1 wherein the spring means includes first and second extension spring members connected to the driven element of the eddy current coupling such that the first extension spring member is effective when the driven element rotates in a first circumferential direction, and the second exten- 10 1 sion springmember is effective when the driven element rotates in a direction opposite to the first circumferential direction.

6. The elevator system of claim 1 wherein the switch means includes a predetermined plurality of pairs of switches, and the cam means includes a like plurality of cam members, each of said cam members being associated with a different pair of switches, with each cam member defining first and second cam surfaces for op erating a predetermined switch of the pair with one cam surface when the car is moving in one direction, and for operating the remaining switch of the pair with the other cam surface when the car is moving in the opposite direction.

7. A speed sensor, comprising:

a supporting structure,

an electroconductive driving element,

a magnetic field producing driven element,

said driving and driven elements being mounted for rotation on said supporting structure on first and second spaced, parallel shaft members, respectively, with the spacingbeing selected such that the driven element establishes a magnetic field which links said driving element,

means translating a predetermined external movement to rotation of said drivingelement, with the rotation of said driving element producing an an gular movement of said driven element due to the magnetic coupling,

cam means mounted on the second shaft member to provide at least a partial counterbalancing relationship with the magnetic field producing driven element,

switch means carried by said support structure and disposed to be operated by said cam means from a first to a second condition at a first predetermined rotational speed of the driving element, as the speed of the driving element is increasing, and back to its first condition at a second predetermined rotational speed of the driving element when the speed of the driving element is decreasing,

and springs associated with the driven element to provide a retarding force on the driven element when the speed of the driving element is increasing, and a restoring force on the driven element when the speed of the driving element is decreasing, to reduce the difference between the first and second predetermined speeds of the driving element at which the switch means operates.

8. The speed sensor of claim 7 wherein any unbalance between the cam means and the magnetic field producing driven element about the second shaft member favors the cam means to direct the field producing driven element to a predetermined angular location about the second shaft member when the driving element is at rest.

9. The speed sensor of claim 7 wherein the switch means inciudes first and second swab E556 the cam means includes a single member having first and second cam surfaces disposed to operate the first and second switches, respectively, when the elevator car is moving in first and second directions, respectively.

10. The speed sensor of claim 7 wherein the magnetic field producing element is fixed to the shaft member by a first support member which extends perpendicularly outward from the shaft member, and the cam means is fixed to the shaft member by a second support member I 1 1 which extends perpendicularly outward from the shaft member in a direction from the shaft member which is opposite to the direction of the first support member.

11. The speed sensor of claim 7 wherein the magnetic bers connected to the driven element such that the first extension spring member is effective when the driven element rotates in a first cicumferential direction, and the second extension spring member is effective when the driven element rotates in a direction opposite the first circumferential direction.

13. the speed sensor of claim 7 wherein the switch means includes a predetermined plurality of pairs of switches, and the cam means includes a like plurality of cam members, each of said cam members being associated with a different pair of switches, with each cam member defining first and second cam surfaces for operating a predetermined switch of the pair with one cam surface when the driving element is rotating in one circumferential direction, and for operating the remaining switch of the pair with the other cam surface when the driving element is rotating in the opposite circumferential direction. 

1. An elevator system, comprising: an elevator car, means for moving said elevator car in a predetermined path, speed sensor means including an eddy current coupling having rotatable driving and driven elements, means translating movement of said elevator car into rotational movement of said driving element, said driven element including a shaft member mounted for rotation, a magnetic field producing element, and cam means, said magnetic field producing element and said cam means being mounted on said shaft member to provide at least a partial counterbalancing relationship therebetween, switch means disposed to be operated from a first condition to a second condition by said cam means at a first predetermined speed of the elevator car when the elevator car is accelerating, and back to its first predetermined condition at a second predetermined speed when the elevator car is decelerating, control means responsive to the condition of said switch means, said means for moving said elevator car in a predetermined path being responsive to said control means, and spring means associated with said driven elements to provide retarding and restoring forces thereon when the speed of the elevator car is increasing and decreasing, respectively, to reduce the difference between the first and second predetermined speeds of the elevator car at which the switch means operates.
 2. The elevator system of claim 1 wherein the switch means includes first and second switches and the cam means includes a single member having first and second cam surfaces disposed to operate the first and second switches, respectively, when the elevator car is moving in first and second directions, respectively.
 3. The elevator system of claim 1 wherein the magnetic field producing element is fixed to the shaft member by a first support member which extends perpendicularly outward from the shaft member, and the cam means is fixed to the shaft member by a second support member which extends perpendicularly outward from the shaft member in a direction from the shaft member which is opposite to the direction of the first support member.
 4. The elevator system of claim 1 wherein the magnetic field producing element and cam means are spaced from their supporting shaft member on opposite sides thereof, with the spring means being disposed to apply its retarding and restoring forces to a predetermined point between the shaft member and the cam means.
 5. The elevator system of claim 1 wherein the spring means includes first and second extension spring members connected to the driven element of the eddy current coupling such that the first extension spring member is effective when the driven element rotates in a first circumferential direction, and the second extension spring member is effective when the driven element rotates in a direction opposite to the first circumferential direction.
 6. The elevator system of claim 1 wherein the switch means includes a predetermined plurality of pairs of switches, and the cam means includes a like plurality of cam members, each of said cam members being associated with a different pair of switches, with each cam member defining first and second cam surfaces for operatiNg a predetermined switch of the pair with one cam surface when the car is moving in one direction, and for operating the remaining switch of the pair with the other cam surface when the car is moving in the opposite direction.
 7. A speed sensor, comprising: a supporting structure, an electroconductive driving element, a magnetic field producing driven element, said driving and driven elements being mounted for rotation on said supporting structure on first and second spaced, parallel shaft members, respectively, with the spacing being selected such that the driven element establishes a magnetic field which links said driving element, means translating a predetermined external movement to rotation of said driving element, with the rotation of said driving element producing an angular movement of said driven element due to the magnetic coupling, cam means mounted on the second shaft member to provide at least a partial counterbalancing relationship with the magnetic field producing driven element, switch means carried by said support structure and disposed to be operated by said cam means from a first to a second condition at a first predetermined rotational speed of the driving element, as the speed of the driving element is increasing, and back to its first condition at a second predetermined rotational speed of the driving element when the speed of the driving element is decreasing, and springs associated with the driven element to provide a retarding force on the driven element when the speed of the driving element is increasing, and a restoring force on the driven element when the speed of the driving element is decreasing, to reduce the difference between the first and second predetermined speeds of the driving element at which the switch means operates.
 8. The speed sensor of claim 7 wherein any unbalance between the cam means and the magnetic field producing driven element about the second shaft member favors the cam means to direct the field producing driven element to a predetermined angular location about the second shaft member when the driving element is at rest.
 9. The speed sensor of claim 7 wherein the switch means includes first an second switches and the cam means includes a single member having first and second cam surfaces disposed to operate the first and second switches, respectively, when the elevator car is moving in first and second directions, respectively.
 10. The speed sensor of claim 7 wherein the magnetic field producing element is fixed to the shaft member by a first support member which extends perpendicularly outward from the shaft member, and the cam means is fixed to the shaft member by a second support member which extends perpendicularly outward from the shaft member in a direction from the shaft member which is opposite to the direction of the first support member.
 11. The speed sensor of claim 7 wherein the magnetic field producing element and cam means are spaced from their supporting shaft members on opposite sides thereof, with the spring means disposed to apply its retarding and restoring forces to a predetermined point between the shaft member and the cam means.
 12. The speed sensor of claim 7 wherein the spring means includes first and second extension spring members connected to the driven element such that the first extension spring member is effective when the driven element rotates in a first cicumferential direction, and the second extension spring member is effective when the driven element rotates in a direction opposite the first circumferential direction.
 13. the speed sensor of claim 7 wherein the switch means includes a predetermined plurality of pairs of switches, and the cam means includes a like plurality of cam members, each of said cam members being associated with a different pair of switches, with each cam member defining first and second cam surfaces for operating a predetermined switch of the pair with one cam surface when the driving element is rotating in one circumferential direction, and for operating the remaining switch of the pair with the other cam surface when the driving element is rotating in the opposite circumferential direction. 